Fix rooms v3 url paths for good - with tests (#1130)

* Fix rooms v3 url paths for good - with tests

- Add a test rig around `federationapi` to test routing.
- Use `JSONVerifier` over `KeyRing` so we can stub things out more easily.
- Add `test.NopJSONVerifier` which verifies nothing.
- Add `base.BaseMux` which is the original `mux.Router` used to spawn public/internal routers.
- Listen on `base.BaseMux` and not the default serve mux as it cleans paths which we don't want.
- Factor out `ListenAndServe` to `test.ListenAndServe` and add flag for listening on TLS.

* Fix comments

* Linting

federationapi/routing/send_test.go

@@ -10,6 +10,7 @@ import (
 
 	eduAPI "github.com/matrix-org/dendrite/eduserver/api"
 	fsAPI "github.com/matrix-org/dendrite/federationsender/api"
+	"github.com/matrix-org/dendrite/internal/test"
 	"github.com/matrix-org/dendrite/roomserver/api"
 	"github.com/matrix-org/gomatrixserverlib"
 )
@@ -53,15 +54,6 @@ func init() {
 	}
 }
 
-type testNopJSONVerifier struct {
-	// this verifier verifies nothing
-}
-
-func (t *testNopJSONVerifier) VerifyJSONs(ctx context.Context, requests []gomatrixserverlib.VerifyJSONRequest) ([]gomatrixserverlib.VerifyJSONResult, error) {
-	result := make([]gomatrixserverlib.VerifyJSONResult, len(requests))
-	return result, nil
-}
-
 type testEDUProducer struct {
 	// this producer keeps track of calls to InputTypingEvent
 	invocations []eduAPI.InputTypingEventRequest
@@ -330,7 +322,7 @@ func mustCreateTransaction(rsAPI api.RoomserverInternalAPI, fedClient txnFederat
 		context:    context.Background(),
 		rsAPI:      rsAPI,
 		eduAPI:     &testEDUProducer{},
-		keys:       &testNopJSONVerifier{},
+		keys:       &test.NopJSONVerifier{},
 		federation: fedClient,
 		haveEvents: make(map[string]*gomatrixserverlib.HeaderedEvent),
 		newEvents:  make(map[string]bool),